Dental imaging of internal tooth structure is conventionally accomplished by using a source of soft x-rays projected through the teeth of a patient. Also using projection of light in the visible spectrum are dental procedures for whitening teeth as well as hardening material to make dental impressions.
The x-ray projection device generally is large and cumbersome and projected externally to the head of a patient through a determined position on the patient's jaw. Sensitive film material is placed behind a tooth or series of teeth at the desired location, thereby forming a shadow image on the film from the x-rays which penetrate through the teeth from the projection device.
Thereafter, the exposed film then needs to be developed, using chemical or other processes before the results can be viewed by the dentist. This procedure exposes both the x-ray technician and the patient to irradiated x-rays and is slowed by the need to develop the film.
Newer technology makes use of charge coupled devices (CCDs) instead of film material. Such devices receive the x-rays transmitted through the teeth from the projection device and allow for the digitizing of the tooth pictures allowing for immediate display and imaging of the results on a monitor after x-ray exposure. This technique, while faster, also causes the patient and the technician to be exposed to X-ray radiation at other unwanted parts of the body, which may be dangerous.
Dental impressions are still commonly handled by making negative castings of a section or all of the dental arch. Conventionally, casting material made from kelp or other material which hardens using a catalyst is used for making the negative impression of the teeth. Generally the casting material is mixed with a catalyst and then used to fill a dental tray selected to fit the patient's mouth dimensions. The selected tray, filled with the impression material, is then placed in the mouth wherein the patient sinks his teeth into the material down to the gum line. After about 3–5 minutes the impression material is removed from the teeth and a negative impression is formed therein from which a positive model of the teeth can be obtained using other molding material. The catalyst for the impression material can either be chemical or just as in the case of dental surface whitening, it may be light activated.
The herein described apparatus and method provide for the projection of energy at determined wavelengths to the task in the visible and invisible spectrum at low energy with great specificity as to location. This removes, or at least considerably diminishes, the radiation hazard to the patient and technician and makes real-time imaging of internal teeth structures possible. In addition to imaging, the described apparatus can also provide additional functions common to modern dentistry through the provision of projected light at wavelengths that cure impression material and/or tooth filling material and/or activate teeth whitening compounds.
There are many liquid and semi-liquid materials which can be activated by irradiation with high-energy photons. The incident radiation at a determined wavelength initiates an intended chemical chain reaction in these materials or compounds causing them to cure or harden. Such materials are also conventionally used for commercial applications such as light activated curing of sealants for parts assemblies.
In dentistry such photon induced curing of compounds is commonly used for filling cavity and repair of tooth chips and external tooth surfaces and the like. The same curing technique is also used for making dental impressions of a patient's mouth and tooth structure and is also used to activate teeth whitening substances such as hydrogen peroxide compounds containing photon sensitive accelerator materials.
Conventional photon sources for such curing processes are emitting in the visible or UV portion of the energy spectrum. While early photon sources made use of halogen tubes and bulky, high voltage gas lasers, newer devices make use of light emitting diodes (LED), and diode lasers. These latter devices allow for the design of a more compact, low voltage curing apparatus and one which has better efficiency in converting input power to light output power. The wavelength required in such curing and whitening equipment and procedures is dictated by the material used and that compound's spectral absorption characteristics, which generally tend to be rather specific.
U.S. Pat. No. 6,102,696 (Osterwalder)teaches a self contained light source for curing light initiated resins used to coat teeth as veneers and fill cavities and chips in teeth in aesthetic or restorative procedures. Osterwalder, while providing a great leap forward in utility and convenience in the curing of such dental material, is intended for curing in small specific areas and not intended to provide imaging.
U.S. Pat. No. 6,077,073 (Jacob) relates to an elongated sheathed light emitting diode array apparatus which is also specifically designed for curing resins in dentistry for localized fillings in cavities. Jacob too lacks registration of the projected photons to an imaging device and would not be suitable for such applications as imaging. Nor would Jabob be suitable for curing of impressions and activating whitening agents, which are discussed herein. Such applications require an apparatus designed to form images from a specific projection point on a specific registered reception point and also to activate and cure compounds which are spread over large areas and are applied in thicker layers than those applied for cavity filling purposes.
U.S. Pat. No. 5,316,473 (Hare) teaches a device for light curing of a large area in the mouth. However, Hare teaches the use of either fiber optics or LEDs which are not powerful enough nor very efficiently directed towards the desired areas. Hare thus suffers from the same drawback of ineffective application of the curing light source and of insufficient power density for curing/whitening of thick layers of compounds. Furthermore, this apparatus is of rigid design and requires the fabrication of several different models of trays to accommodate all possible dental shapes.
As such, there is a need for further improvements of the state of the art in creating novel dental imaging and curing equipment. Such a device should be flexible and require low voltage while still being capable of irradiating large areas of the dental arch for impression curing and/or whitening. Such a device should provide for a short cure-time and an irradiation which is capable to penetrate deep into the material to be activated. Further, such a device should provide an accurate and easily maintained registration of an image sensing means with the projection of irradiation to provide sharp real time imagery of the teeth.